1. Field of the Invention
The present invention relates to an image data processing apparatus, image data processing method, and program which perform the image data process of rotating a display image.
2. Description of the Related Art
Conventionally, an image data processing apparatus, which performs a rotation on a display image, needs a page memory for storing one-page image data of the display image before carrying out the rotation, and a page memory for storing one-page image data of the display image after the rotation. However, since the amount of data contained in an image has been growing due to increasing resolution of a display image, a page memory having a large storage capacity is necessary for the rotation of the display image. The page memory needs storage capacity for storing two-screen image data, resulting in a considerable increase in cost. As a solution to this problem, the following image data processing method which performs an image rotation on image data has been proposed. That is, a restart marker as a JPEG control code is added to JPEG compression-coded image data and compressed image data is decoded for each stripe having a predetermined width. Accordingly, a method for reducing the storage capacity of a buffer memory necessary for storing the decoded image data has been proposed.
The following method has also been proposed. An image data processing apparatus, which can perform a rotation on a display image, divides input image data into bands, rearranges the reading order of the band-divided image data in accordance with the rotation angle, and performs a compression process for each band. This eliminates the necessity of performing skip reading of compressed code in a decompression process for image data, thereby enabling a decompression process to be performed in real time.
However, a conventional image data processing apparatus such as a digital camera cannot decompress original image data that is compression-coded by a JPEG compression scheme, rotating the decompressed image data, and then recording the rotated image data.    [Patent Reference 1] Japanese Patent Laid-Open No. 09-247423    [Patent Reference 2] Japanese Patent Laid-Open No. 2003-092674